Celotex Is Now SOPRATHERM: What the Name Change Means for UK Customers

Celotex insulation products are now part of SOPREMA UK, and the familiar Celotex PIR insulation range is being sold under the SOPRATHERM name.

For example:

• Celotex GA4000 is now SOPRATHERM GA4000
• Celotex TB4000 is now SOPRATHERM TB4000
• Celotex XR4000 is now SOPRATHERM XR4000
• Celotex CW4000 is now SOPRATHERM CW4000
• Celotex PL4000 is now SOPRATHERM PL4000

For builders, tradespeople, merchants and homeowners who have used Celotex for years, the most important thing to understand is that this is primarily a brand and product-name transition rather than the disappearance of the familiar insulation range.

SOPREMA UK says the former Celotex product range, technical information and support are now available through SOPREMA UK, with some product names and locations of technical information changing while the established product performance and expertise remain.

Why has Celotex changed its name?

The change is part of a wider restructuring by SOPREMA UK.

SOPREMA announced in September 2025 that it would bring several of its UK construction brands together under one identity from 1 January 2026.

This included:

• Celotex
• Chesterfelt
• YBS Insulation

Rather than operating these as separate brands, SOPREMA decided to integrate them into a broader SOPREMA UK product portfolio. The company said the objective was to make its products and services easier for customers to access through a single organisation.

Celotex itself had been acquired by SOPREMA in 2024.

The result is that the Celotex name is gradually disappearing from packaging and product listings, while many of the products customers already recognise continue under SOPRATHERM branding.

Is SOPRATHERM the same as Celotex?

For the established ranges being renamed, customers should think of SOPRATHERM as the successor branding to Celotex rather than as an unfamiliar alternative insulation manufacturer.

For example, SOPREMA lists:

SOPRATHERM GA4000 — previously Celotex GA4000

The product remains a foil-faced rigid PIR insulation board with a declared thermal conductivity of 0.022 W/mK, designed for applications including pitched roofs, floors and dry lining.

Similarly:

SOPRATHERM TB4000 — previously Celotex TB4000

remains a foil-faced PIR insulation board with a declared thermal conductivity of 0.022 W/mK.

Distributor CCF has described the change to customers in similarly straightforward terms, saying that the PIR boards customers use remain the same while product names and packaging are updated.

So if you normally buy Celotex GA4000 and your merchant supplies SOPRATHERM GA4000 instead, the different logo does not in itself mean you have received an alternative product.

Celotex to SOPRATHERM product name guide

Here are some of the key changes customers are likely to encounter:

Previous name	New name	Typical use
Celotex TB4000	SOPRATHERM TB4000	Thin PIR insulation for floors, roofs and dry lining
Celotex GA4000	SOPRATHERM GA4000	General-purpose PIR for floors, roofs and walls
Celotex XR4000	SOPRATHERM XR4000	Thicker PIR insulation for higher thermal requirements
Celotex CW4000	SOPRATHERM CW4000	Partial-fill masonry cavity walls
Celotex CW4000 FF	SOPRATHERM CW4000 FF	Full-fill masonry cavity walls
Celotex PL4000	SOPRATHERM PL4000	PIR insulation bonded to plasterboard

In many cases, SOPREMA has deliberately retained the familiar product codes.

That should make the transition considerably easier for contractors and merchants.

Someone who has specified GA4000, for example, does not have to learn an entirely new product numbering system. Instead, Celotex GA4000 becomes SOPRATHERM GA4000.

What is SOPRATHERM GA4000?

GA4000 has long been one of the better-known Celotex products, so its change of branding is likely to be one of the most noticeable.

It is now sold as SOPRATHERM GA4000.

SOPREMA describes it as a rigid polyisocyanurate, or PIR, insulation board with aluminium foil facings.

It has a declared thermal conductivity of 0.022 W/mK and is available in a range of thicknesses. Its defined applications include pitched roofs, floors and dry lining, subject to the appropriate specification and certification requirements.

For customers searching online for terms such as:

“Celotex GA4000”

“Celotex 50mm”

“Celotex 75mm”

or

“Celotex 100mm”

they may therefore increasingly encounter SOPRATHERM-branded products instead.

What is SOPRATHERM TB4000?

Celotex TB4000 has become SOPRATHERM TB4000.

TB4000 covers thinner PIR insulation boards and, according to SOPREMA, is available in thicknesses from 20mm to 40mm.

It has a declared thermal conductivity of 0.022 W/mK and can be used in defined applications including pitched roofs, dry lining and floors.

The TB4000 name has therefore been retained, making it relatively easy for existing Celotex customers to recognise the equivalent product.

What is SOPRATHERM XR4000?

The former Celotex XR4000 range is now SOPRATHERM XR4000.

XR4000 covers thicker rigid PIR boards, with SOPREMA currently listing thicknesses from 110mm to 200mm.

Like GA4000, its declared thermal conductivity is 0.022 W/mK and its defined applications include floors, pitched roofs and dry lining.

The thicker boards can be particularly relevant where a construction needs greater insulation thickness to achieve the required thermal performance.

What has happened to Celotex cavity-wall insulation?

The familiar cavity-wall products have also moved across to the SOPRATHERM brand.

Celotex CW4000 is now SOPRATHERM CW4000.

It is intended for partial-fill masonry cavity-wall applications. SOPREMA lists a declared thermal conductivity of 0.022 W/mK.

There is also SOPRATHERM CW4000 FF, previously Celotex CW4000 FF, for defined full-fill masonry cavity applications.

Again, retaining the CW4000 designation should help specifiers and installers identify the product they previously knew under the Celotex brand.

Has Celotex insulated plasterboard changed too?

Yes, the branding has changed here as well.

Celotex PL4000 is now SOPRATHERM PL4000.

This product combines a PIR insulation core with 12.5mm tapered-edge plasterboard, creating an insulated plasterboard product suitable for defined applications such as internal wall dry lining and pitched-roof ceiling applications.

The PIR component has a declared thermal conductivity of 0.022 W/mK.

Anyone searching for Celotex insulated plasterboard may therefore start seeing SOPRATHERM PL4000 appearing in merchant listings instead.

Can you still buy Celotex?

This is where the terminology can become confusing.

Customers may still refer to the product as Celotex, merchants may continue receiving searches and enquiries for Celotex, and existing stock or online pages may still display the old name.

But the manufacturer is moving the range under the SOPREMA UK identity.

SOPREMA's own website now directs people searching for Celotex insulation to the former Celotex range within SOPREMA UK and states that some product names have changed.

Over time, customers should therefore expect SOPRATHERM and SOPREMA to become the names they see more frequently when buying the products previously sold as Celotex.

Why keep names such as GA4000 and TB4000?

Retaining familiar product designations is useful because these codes are deeply embedded in the UK construction industry.

They appear in:

• architectural specifications
• builders' merchant listings
• quotations
• construction drawings
• product comparisons
• invoices
• contractors' material lists
• online searches

Completely replacing both the Celotex brand and product code at the same time could create significant confusion.

Calling the new product SOPRATHERM GA4000, rather than replacing GA4000 with an entirely new designation, makes it much easier to identify the corresponding product.

What does the change mean for builders and contractors?

For most contractors, the immediate practical impact should be relatively small.

The main adjustment will be becoming familiar with SOPRATHERM appearing where they previously expected to see Celotex.

A contractor ordering GA4000 may receive a board marked SOPRATHERM GA4000. Someone searching for a Celotex technical document may increasingly find it through the SOPREMA UK website.

There may therefore be a period where both names are commonly used in conversation.

A builder might ask a merchant for “Celotex,” while the quotation or delivery note identifies the product as SOPRATHERM.

Knowing that the range has been rebranded should avoid unnecessary concern when this happens.

What does the change mean for homeowners?

Homeowners carrying out extensions, renovations, loft conversions or other insulation projects may be more confused by the change because they are less likely to follow building-product industry news.

For example, a homeowner may receive a quote specifying:

100mm Celotex GA4000

but subsequently see:

100mm SOPRATHERM GA4000

when searching for the product or receiving a delivery.

The important thing is not to rely on the brand name alone.

Check the complete product designation, thickness, technical performance, certification and intended application against the specification for the project.

Where there is any uncertainty, the builder, architect, merchant or manufacturer's technical team should confirm the appropriate product.

Does the rebrand affect technical documentation?

Technical information previously associated with Celotex is moving to SOPREMA UK's resources.

SOPREMA says technical datasheets, declarations, certificates and other documentation for the former Celotex products can now be found through its product pages and technical-document resources.

This is particularly important for architects, building-control professionals and contractors.

An old project specification might reference Celotex, while the current documentation carries SOPRATHERM or SOPREMA branding.

Always use the current technical documentation for the exact product being installed, particularly where Building Regulations, fire performance, thermal calculations or third-party certification are relevant.

Is SOPRATHERM still PIR insulation?

Yes.

Products including SOPRATHERM GA4000, TB4000, XR4000 and CW4000 are rigid polyisocyanurate (PIR) insulation boards.

PIR insulation is widely used in UK construction because it provides relatively high thermal resistance for its thickness.

That makes it useful in applications where achieving the necessary insulation performance without creating an excessively thick wall, roof or floor build-up is important.

However, the appropriate insulation material depends on the building and application, and products must always be specified and installed in accordance with the relevant regulations, certification and manufacturer's instructions.

Do Building Regulations still apply in exactly the same way?

A change of name does not remove any of the normal responsibilities surrounding insulation specification.

The correct product must still be selected for the application.

SOPREMA specifically advises that its products should be specified and installed in accordance with applicable Building Regulations, statutory guidance and relevant standards.

There are also application-specific restrictions that need to be considered.

For example, SOPREMA states on several SOPRATHERM product pages that the products should not be used in external walls of relevant buildings over 11 metres where current combustibility requirements apply.

Anyone working on a regulated or technically complex project should therefore consult the current product documentation rather than assuming suitability because they have previously used a Celotex-branded board.

Who is SOPREMA?

Although the SOPREMA name may be less familiar to some UK homeowners than Celotex, SOPREMA is a major international construction-products business.

The company produces solutions across areas including:

• thermal insulation
• waterproofing
• roofing systems
• acoustic insulation
• civil engineering products
• building-envelope systems

The integration of Celotex is intended to create a broader UK offering under the SOPREMA name rather than operating Celotex as a standalone brand.

Why the change could cause confusion in 2026

Celotex has been such a recognisable insulation name in Britain that it is likely to remain part of everyday construction vocabulary for some time.

In much the same way that a well-established brand name can become shorthand for a type of product, builders may continue asking for “Celotex” even as the packaging moves to SOPRATHERM.

This means three names may appear during conversations about the products:

Celotex — the familiar former brand.

SOPRATHERM — the new name used for the PIR product ranges.

SOPREMA — the parent brand and company bringing the portfolio together.

The easiest way to remember the transition is:

Celotex is now part of SOPREMA UK, and the familiar Celotex PIR ranges are becoming SOPRATHERM products.

Celotex vs SOPRATHERM: frequently asked questions

Is Celotex now called SOPRATHERM?

The familiar Celotex PIR range is transitioning to the SOPRATHERM name as Celotex becomes integrated into SOPREMA UK. Products such as Celotex GA4000 are now listed as SOPRATHERM GA4000.

Is SOPRATHERM GA4000 the same as Celotex GA4000?

SOPREMA identifies SOPRATHERM GA4000 as previously Celotex GA4000. The product remains a foil-faced PIR insulation board with a declared thermal conductivity of 0.022 W/mK.

What is Celotex TB4000 called now?

Celotex TB4000 is now SOPRATHERM TB4000.

What is Celotex XR4000 called now?

Celotex XR4000 is now SOPRATHERM XR4000.

What is Celotex CW4000 called now?

Celotex CW4000 is now SOPRATHERM CW4000.

What is Celotex PL4000 called now?

Celotex PL4000 insulated plasterboard is now SOPRATHERM PL4000.

When did Celotex change to SOPREMA?

SOPREMA UK announced that its brand unification would take effect from 1 January 2026, bringing Celotex and several other brands under the SOPREMA UK identity.

Can I still ask a builders' merchant for Celotex?

Many people within the industry will undoubtedly continue using the Celotex name during the transition. However, customers should increasingly expect to see SOPRATHERM branding on the equivalent ranges.

The bottom line

The appearance of SOPRATHERM instead of Celotex may look like a major change, but for customers the transition is much simpler than it first appears.

Celotex has been integrated into SOPREMA UK, and many of the familiar Celotex insulation ranges now carry the SOPRATHERM name.

The recognisable product codes have largely survived the transition:

GA4000 remains GA4000.
TB4000 remains TB4000.
XR4000 remains XR4000.
CW4000 remains CW4000.
PL4000 remains PL4000.

The name on the board is changing, but customers who have relied on these familiar Celotex ranges should be able to identify their SOPRATHERM equivalents relatively easily.

For any new project, however, always check the current SOPREMA technical documentation, certification and application guidance for the exact product being specified or installed.